Loop excision of the cervix and the risk of preterm delivery

Posted 11 years ago

When asked by my patients whether a LLETZ or cone bipopsy impacted on the risk of a preterm delivery on a subsequent pregnancy, often I became a bit vague in the past. 

I did not know the exact percentages, numbers and facts that I like so much to quote when explaining risks to my patients.

Until I came across a recent Finnish paper published in Obstetrics and Gynecology on the risk of preterm delivery after LLETZ. This paper answered my questions. Now I can put the risk into real numbers and give it a bit more three-dimensional shape.

The authors from Finnland wanted to quantify the impact of a LLETZ (they called it LEEP) on the incidence of preterm delivery, what the impact of a repeat LLETZ on the incidence of preterm delivery was and whether the severity of the cervical lesion had an impact on the incidence of preterm delivery.

They conducted a data linkage study on women, 15 to 49 years of age who had a LLETZ. They combined data from hospital discharges with data from the Medical Birth Register. Data testing outside this research setting confirmed that data of only 0.1% of all newborns were missing from the register. Only singleton deliveries were included.

The “case” group consisted of 20,011 women who had a total of 25,101 LLETZs from 1997 to 2009. Of these, 5,114 women had a subsequent singleton delivery. The “controls” consisted of 430,975 women with no previous LLETZ and 658,179 singleton deliveries.

Preterm delivery was defined as delivery before 37 weeks of gestation. Extreme preterm delivery was defined as delivery before 28 weeks of gestation. Low birth weight was defined as less than 2500 grams and perinatal deaths were defined as deaths from 22 weeks of gestation until one week post partum.

Women’s mean age was 30 years in both groups. Expectedly, women with LLETZ were more often smokers and continued to smoke throughout their pregnancy.

• Women with LLETZ had a preterm delivery rate of 7.2%, which is 60% higher than women who did not have a LLETZ (4.6%).
• The severity of cervical dysplasia did not increase the risk of preterm delivery. However, the presence of cervical cancer increased the risk of preterm delivery 2.5 fold
• A repeat LLETZ increased the risk of preterm delivery almost 3-fold (odds ratio 2.8).
• A previous LLETZ did not increase the risk of extremely preterm delivery, low birth weight nor the risk for perinatal death.
• The time between LLETZ and delivery did not impact on the preterm delivery incidence.

The study results appear very robust. They have been obtained on a population level; these data are almost certainly accurate reflecting the Finnish population and we can assume that these data are applicable to other countries as well.

What do we learn from this study?

The risk of LLETZ (even for diagnostic LEEP) increased the risk of preterm delivery by 60% and a repeat LLETZ had a substantial impact on the preterm delivery rate.

The diagnostic LLETZ/LEEP should not be done. Nowadays, a cervical biopsy will determine the pathological diagnosis in the majority of patients.

A LEEP in young women may have consequences and we need to inform patients about the risk of preterm delivery. Now we can even quantify the risk: 60% increased for a “standard” LLETZ – threefold risk if the LLETZ is performed for cancer or for a repeat LLETZ.

Delaying a Re-LLETZ does not lower the risk of preterm delivery.

I also learned that I like to know. Knowing what the percentage is of clear margins after LLETZ; how low the rate of recurrence a year after LLETZ is in my hands; even simpler - how many of these operations have I done in the last year, last two years. 

Believe you are a great surgeon? Know it. 

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